An optical disk drive of slot-in type is generally installed in a notebook computer or in an audio-and-video instrument of an automobile for reproducing the information recorded in an optical recording media, such as playing songs from a CD.
Referring to FIGS. 1 and 2, perspective and bottom views of a conventional disk drive of slot-in type are shown to include a casing formed with a disk entrance-and-exit slot 3, and a disk transport mechanism 6 disposed in the casing adjacent to the entrance-and-exit slot 3. The disk transport mechanism 6 includes an upwardly biased roller-mounting frame 606 pivoted to a plate member 8 of the disk drive 2 via a frame-mounting shaft 12. A disk transport roller 602 is journalled to an inner end of the roller-mounting frame 606 (see also in FIG. 3A) and generally contacts slidably the plate member 8 by virtue of upwardly biased action of a spring. The disk transport roller 602 has a coupling end exposed from the roller-mounting frame 606 (see FIG. 2). The disk transport mechanism 6 further includes a gear transmission system 14 and a driving motor 10. The gear transmission system 14 includes a driven gear 604 fixed to the coupling end of the transport roller 602, and a driving gear 1402 meshed with the driven gear 604. Since the driving gear 1402 is operably associated with the driving motor 10, actuation of the latter results in rotation of the disk transport roller 602. Under this condition, when an optical disk 4 is between the plate member 8 and the transport roller 602 via the entrance-and-exit slot 3 (see FIG. 3B), the optical disk 4 will be drawn into or ejected from the disk drive 2 upon rotation of the transport roller 602 due to applying force on the optical disk 4. The roller-mounting frame 606 further moves to allow the transport roller 602 to shift to a lower position against the urging force of the spring, thereby spacing the transport roller 602 apart from the disk 4 when the optical disk 4 is moved to a reading position (see FIG. 3C).
Some disadvantages resulting from the use of the aforesaid conventional disk drive are as follows:                (a) The transport roller 602 is susceptible to wear due to constant contact with the plate member 8 when they are not spaced apart by a disk;        (b) The driving and driven gears 1402, 604 cooperatively define a first distance L1 between the axes thereof when the transport roller 602 contacts the plate member 8;        (c) During the disk ejecting and drawing in operation, the driving and driven gears 1402, 604 cooperatively define a second distance L2. It is note that L2>L1 due to presence of the disk between the transport roller 602 and the plate member 8. In other words, it can be assumed that the driving and driven gears 1402, 604 are not fully meshed with each other during the disk ejecting or drawing in operation. Under such condition, the transport roller 604 may wobble with respect to the disk 4.        